To prevent mis-connection of a fluid line to a device containing a particular medication, it has been shown in the prior art that a connector may be made up of two portions, with the portions being connected by complementary configured opposing surfaces. Such two portions connector ensures that the one line from one portion of the connector would not be wrongly connected to a different medication line. A fastening mechanism comprised of such complementary connecting portions is disclosed in U.S. Pat. No. 6,612,624 and its parent patent U.S. Pat. No. 6,402,207. The '624 patent discloses in particular a ratchet mechanism, as part of the connector, that prevents or impedes the uncoupling of one portion of the connector from a syringe to which the other portion may be connected. In practice, since the ratchet mechanism is dependent on the interaction of the teeth on the inner surface of an outer sleeve with a pawl of an inner body that fits into the outer sleeve, if the syringe were to be tightened too forcefully, the inner body would pop out of the outer sleeve. Moreover, as disclosed in the '624 patent, the ratchet mechanism is a portion of the connector that does not fully isolate the relative rotation of the outer sleeve and the inner body.